Thanks to everyone here, as a pensioner these are expensive batteries with technology I don't understand, yes the inverter is for field work, I am going to Glencoe area here in scotland for my real passion of filming, I plan to use p2v for a lot of difficult areas, l am currently practising filming close in to objects but at a range of around 500 ft, this little flying machine is very much fitting the bill, once again thanks I. really appreciate your replies and interest